Field of the Invention
The present invention relates to a reciprocating internal combustion engine and particularly to an engine of the two-cycle type.
One of the primary problems of small two cycle engines is the difficulty in providing adequate lubrication, and for this reason it has often been necessary to mix oil with the gasoline. Although this assures some degree of lubrication between the sliding surfaces of the piston and cylinder, it adds a significant amount of contaminants to the fuel which prevents clean burning thereof and causes the exhaust to be quite smoky.
A further problem with many prior art two cycle engines is the difficulty in accomplishing good scavenging of the exhaust gases prior to compression of the fresh charge. If too great a portion of the exhaust gases remain in the combustion chamber, a loss of power will result. On the other hand, if a portion of the fresh charge is vented to the atmosphere during scavenging, this will reduce fuel economy and also develop pollutants.
One example of a prior art engine which is related to the present invention is disclosed in U.S. Pat. Nos. 2,319,427 and 2,385,457. The engine is basically a two cylinder reciprocating engine having opposing cylinders on either side of a power transmitting mechanism with reciprocating pistons received therein and auxiliary compression chambers formed between a pair of stationary pistons and the aforementioned moveable pistons. The fuel is initially compressed in the auxiliary chamber and then admitted to the primary combustion chambers through a back pressure valve and around a deflector plate for the purpose of scavenging the combustion chamber of the exhaust gases and supplying it with a fresh charge of fuel for subsequent compression and ignition.
A further example of prior art two stroke internal combustion engines comprises a single cylinder with a pair of coaxial pistons one of which is free floating, as disclosed in U.S. Pat. No. 1,756,354 to Heibig. In this engine, the fuel/air mixture is drawn into the chamber formed between the two moveable pistons, compressed therein and then injected into the combustion chamber from which the exhaust gases had previously been vented by means of a mechanically opened exhaust valve. Compression and ignition then occurs and the entire cycle is repeated.